In general, a drum type washing machine washes laundry using a force that is generated when the laundry is raised by a lifter and then is dropped down as the drum rotates. The advantages of this drum type washing machine include less damage to the clothing due to less friction, and consumption of less water due to water being primarily at the bottom of the drum.
The drum type washing machine includes a cabinet that forms the exterior of the washing machine; a tub in the cabinet that accommodates water therein; a rotary drum in the tub that holds laundry therein; a motor in, behind or under the tub that provides a motive power to the drum; a water supply device that supplies water to the tub; and a drain that drains the water from the tub to the outside of the cabinet after the washing process is completed.
A detergent case may be at one side of the cabinet, and a water supply pipe may supply water to the tub through the detergent case. As water is supplied through the water supply pipe by the water supply device, detergent in the detergent case is also supplied to the tub along with the water.
A circulation duct for drying the laundry may be at one side of the tub. The circulation duct may have incorporate therein a fan configured to circulate air in the tub; a condensing device configured to condense moisture in the air; and a heating device configured to heat the air after the condensing process. Once the drying process has begun, the air in the tub is brought into the circulation duct by the fan. The air brought into the circulation duct may be subjected to a condensing process for eliminating moisture from the air by the condensing device, and the air may then be heated by the heating device.
Conventionally, the condensing device includes a nozzle at an upper side of the circulation duct, configured to jet coolant directly to the inside of the circulation duct. The coolant from the upper side of the circulation duct freely falls down along the circulation duct, while contacting the air, and lowers the temperature of the ambient air around the circulation duct and/or condenses the moisture in the air flowing in the circulation duct into water droplets. The water droplets may also fall down along the circulation duct and be collected in a separate condensed water tray.
In such a conventional washing machine, moisture can be substantially condensed only for the time during which the jetted coolant actually passes through and contacts the high-temperature and high-humidity air in the circulation duct. As a result, to effectively reduce moisture from the air, the coolant needs to be continuously supplied to the circulation duct. Thus, as compared to the amount of the moisture removed from the air, an excessive amount of coolant is consumed.
In the prior art, there has been an attempt to solve the aforementioned problem by adjusting the timing for supplying the coolant. For example, a method to control the timing for jetting the coolant using a temperature sensor has been proposed. In this method, the temperature sensor has to be installed somewhere in the circulation duct to detect the temperature of the coolant or the air passing through the circulation duct. In this method, the coolant is jetted at a time when the detected temperature reaches a certain temperature.
However, to use such a control method, the temperature sensor needs to be in the circulation duct. As a result, manufacturing cost increases, and the assembly of the circulation duct becomes complicated. Furthermore, if failure in the temperature sensor occurs, the time for jetting the coolant cannot be adjusted.
A conventional drum type washing machine may be disclosed in Korean Patent Application Publication No. 10-2007-0064017.